Patchett et al. in European Patent Application 68,173 disclose that various substituted carboxyalkylamino perhydro-1,4-thiazepin-5-ones and perhydro-1,4-thiazocin-5-ones possess angiotensin converting enzyme inhibition activity.
Meyer et al., "Angiotensin Converting Enzyme Inhibitors:Modifications Of A Tripeptide Analogue", J. Med. Chem., 1982, 25, 996-999, disclose the synthesis and angiotensin converting enzyme inhibition activity of compounds of the formula ##STR2## wherein X can be NH and R can be L-proline.
Almquist et al. in U.S. Pat. No. 4,329,473 disclose oxoalkanoic acid derivatives of L-proline as angiotensin converting enzyme inhibitors.